This invention relates to a flat-panel display structure and a method for making the same and, in particular, to a gas discharge display foraged on a single side of a substrate operable with gases at substantially atmospheric pressure.
Plasma based flat-panel displays have been known since the late 1960's. Broadly, such displays enclose a gas or mixture of gases in a partial vacuum sealed between opposed and crossed ribbons of conductors. The crossed conductors define a matrix of crossover points which are essentially an array of miniature neon picture elements ("pixels") or lamps that provide their own light. At any given pixel, the crossed, spaced conductors act like opposed electrode plates of a capacitor. At each intersection point, a sufficiently large applied voltage causes the gas to break down locally into a plasma of electrons and ions and glow as it is excited by current. Paschen's Law relates the voltage at which a gas breaks down into a plasma, the so called spark or firing voltage, to the product of the pressure of the gas, p (in mm Hg), times the distance, d (in cm), between the electrodes. By scanning the conductors sequentially, a row at a time, with a voltage sufficient to cause the pixels to glow, and repeating the process at least sixty times per second, a steady image can be perceived by the human eye.
These displays have heretofore required that a partial vacuum be established in order to bring the pressure-distance product closer to the region of the so called Paschen minimum firing voltage. The low pressure ambient employed in prior art designs ensured a longer mean free path for liberated electrons by lowering the density of gas molecules in the region between the conductors. The low pressure ambient facilitated higher current levels because the liberated electrons could travel .faster toward other gas molecules and hit them harder to free additional electrons. See S. C. Miller, Neon Techniques and Handling, p. 11 (3d Ed. 1977).
The need to establish a partial vacuum has created manufacturing complexities which have increased the cost of producing flat-panel gas discharge displays. The pressure imbalance between the internal vacuum environment and the external atmosphere has necessitated manufacturing flat-panel displays from reinforced materials so as to withstand the implosive pressure (fifteen pounds per square inch) exerted across the display surface of the panels. Also, rare gases are used for the plasma material which require sophisticated manufacturing facilities. These problems have inspired much of the more recent efforts in the field to look to display structures of other designs including liquid crystals and electroluminescent polymers. See Depp and Howard, Flat-Panel Displays, Scientific American (March 1993) p. 90. Accordingly, it would be advantageous to manufacture a gas discharge flat-panel display operable at atmospheric pressure using air as the operative gas.